Observation of Cu-NMR of CuO2Plane Site in Antiferromagnetic YBa2Cu3O6.1

Abstract

New NMR signals in antiferromagnetic YBa ₂ Cu ₃ O _6.1 with the Néel temperature of T _N =410 K have been observed in the frequency range between 65 MHz and 125 MHz at the zero external field. In corntrast to the nuclear quadrupole resonance (NQR) observed around 30 MHz, the newly observed signals are remarkably dominated by the appearance of the internal field generated by the antiferromagnetic ordering. According to neutron diffraction studies, there exists an antiferromagnetic moment of about 0.6 µ _B on the CuO ₂ plane site. Accordingly, NMR signals are unambiguously assigned to the CuO ₂ plane site and NQR signals around 30 MHz to the CuO chain site. This finding allows us to determine the magnetic phase diagram of YBa ₂ Cu ₃ O _{7- y} from a microscopic point of view.